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심해섭(Hae-Sup Shim) 한국조명·전기설비학회 2017 조명·전기설비학회논문지 Vol.31 No.11
As a result of previous studies [1-2], the warning performances without atmospheric electric field (EF) data are examined by using only intra-cloud (IC) discharges, and cloud-to-ground (CG) strikes data provided by a stand-alone lightning warning system (LWS) during two summers. The warning performances were evaluated by the warning statistics with probability of detection (POD), false alarm ratio (FAR) and critical success index (CSI). Upon conclusion of this study, it was found that removal of EF data from warning conditions decreased FAR to 82%, and increased CSI to 171%, POD to 89% in comparison to the prior study[1]. Therefore, these results mean that IC and CG without EF data were beneficial to an increase in warning performances. However, the stand-alone LWS intended to trigger an only prior warning is not possible to make effective alerts (EA) because there is no effective lead time (LT). Hence, it has still been required to develop the new LWS proposed in the previous study [1] for triggering EA.
낙뢰와 대기전계의 탐지를 기반으로 하는 자동낙뢰경보시스템의 구성과 운용특성
심해섭(Hae-Sup Shim),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2013 조명·전기설비학회논문지 Vol.27 No.11
It is important to give lightning warning prior to a cloud-to-ground (CG) discharge within an Area of Concern (AOC) because most of lightning damage and victim are usually occurred by the first lightning in the AOC. The aim of this study is to find the optimal operation conditions of the automated lightning warning systems in order to make the best use of the available data. In this paper, the test-operated results of the automated lightning alert and risk management system (ALARM) based on detections of CG discharge and eletrostatic field and optimized at probability of lightning have been described. It was possible to obtain the following warning performance parameters: probability of detection (POD), false alarm ratio (FAR), probability of lightning (POL) and failure-to-warn rate (FTW). The data obtained from trial operation for 5months were not sufficient but the first analysis of domestic lightning warning was carried out. We have observed that the evaluated statistical results through trial operation depend on the various factors such as analysis methods and criteria, topographical conditions, etc. Also we suggest some methods for improvement of POL and POD including the finding of the optimal electric field threshold level to be used, based on the high values of FAR and FTW found in this work.
심해섭(Haesup Shim),전태현(Taehyun Jeon) 한국조명·전기설비학회 2009 한국조명·전기설비학회 학술대회논문집 Vol.2009 No.5월
Surge protective devices (SPD) have a special position because of the expectation that they perform an effective protective function against various kinds of surges. However, there exists a misconception that the SPD satisfying lower measured limiting voltage (MLV) should also protect equipment against temporary overvoltages (TOVs) as well. This paper inspects various types of MOV based SPDs and carry out experiments on the side effects of the low MLV characteristics. The experiment results show that a low MLV could cause a higher TOV-induced SPD failure rate in the field.
유효 경보를 위한 새로운 낙뢰 경보시스템의 개발 방법에 대한 제안
심해섭(Hae-Sup Shim),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2015 조명·전기설비학회논문지 Vol.29 No.12
We examine the standalone lightning warning system (LWS) and its warning performances for three years. This system acquires and analyzes the data of cloud-to-ground strike (CG), intra-cloud discharge (IC) and electrostatic field (EF) to produce prior warnings with respect to the impending arrival of CG in the area of concern (AOC). The warnings in this system are carried out based on the fixed two areas method. To evaluate warning performances, we analyzed the statistics of warnings with probability of detection (POD) and false alarm ratio (FAR). Based on the previous study, we revised the trigger and clear conditions of lightning warning for improving the performances of the system. As a result of this revision, POD increased from 0.18 to 0.44 and FAR decreased from 0.96 to 0.78 during the summer of 2014. However, the LWS was not possible to trigger effective alerts (EA) because there was no effective lead time (LT) for the fixed two areas method. Problems related to the low detection efficiency of IC and the use of EF data for warnings still decreased POD and increased FAR. Hence, we proposed the development method of a new LWS (NLWS) that would be composed of integrated weather data, the flexible two areas and the user software in order to trigger EA and improve warning performances.
MOV 기반 서지보호기의 일시과전압 특성에 대한 실험적 연구
심해섭(Haesup Shim),전태현(Taehyun Jeon) 한국조명·전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.1
뇌서지 보호는 오늘날 대부분의 전기전자기기에 있어 중요한 문제 중 하나이다. 그리고 뇌서지 보호를 위한 대다수 SPD의 가장 주요 부품으로 MOV가 사용된다. 본 논문에서는 다양한 타입의 MOV 기반 SPD를 조사하고 낮은 MLV특성의 부작용에 대하여 실험하였다. 실험결과로서 상대적으로 낮은 MLV특성은 실제 현장에서 발생 가능한 TOV 고장 상태하에서 더 큰 고장률로 나타날 수 있으며, 피보호기기보다 우선하여 소손될 수 있음을 알 수 있다. 결국 안전면에서 SPD는 높은 TOV내력과 신속한 단로기의 동작이 요구된다. Protection against lightning surge is an essential part of almost any electrical and electronic equipment today. Metal Oxide Varistor(MOV) is the single most important component in the overwhelming majority of the Surge Protective Devices(SPD) designated to provide such protection. In this paperr various types of MOV based SPD are inspected and experiments are carried out on the side effects of the low Measured Limiting Voltage(MLV) characteristics. Experiment results show that a lower MLV could cause a higher Temporary Overvoltage(TOV)-induced SPD failure rate in the field, and SPD are more likely to be victims rather than protectors in a TOV scenario. This means that from a safety perspective, the SPD should be specified with higher TOV withstand capability(UT) and faster SPD disconnector.
심해섭(Hae-Sup Shim),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2014 조명·전기설비학회논문지 Vol.28 No.9
The aims of this paper are to characterize the transient overvoltages(TOVs) and to evaluate the risk occurring at 22.9kV consumer’s substation. The measurements of lightning- and switching-caused TOVs were made during Mar. 2013 and Feb. 2014. As a consequence, 47 events of TOVs were recorded and 4 of them were higher than the input voltage envelope(IVE) of the information technology industry council(ITI) curve. The measured TOVs are characterized by longer front times and longer durations compared to the 1.2/50㎲ standard impulse voltage waveform, and some of them represent bipolar waves with lower oscillation frequencies. It suggests that the test of non-standard impulse voltage waveforms is needed for effective risk assessments of power apparatus. Lightning- and switching-caused TOVs exceeding IVE of ITI curve are induced at the secondary of 22.9kV potential transformer(PT). We may, therefore, conclude that the surge protection devices should be applied at the secondary of PT and the surge absorbers should be installed at the primary of VCB or PT. The results presented in this paper could be useful to design the reasonable insulation coordination for 22.9kV consumer’s substation.
중성점 비접지 UPS시스템의 부동현상에대한 실험적 연구
심해섭(Hae-Sup Shim) 한국조명·전기설비학회 2011 조명·전기설비학회논문지 Vol.25 No.5
In this study we investigate the background of UPS output transformer(△-Y) operation on neutral ungrounded system, and perform field experiment of neutral floating-phenomenon for the inter-locked securing of electric facilities and improvement of neutral floating-phenomenon. Experiment results show that a floating-phenomenon occurs when four-pole input-breaker trip and the neutral to earth voltage occurring concurrently is identified as phantom voltage. And the measures for the transient overvoltage that can occur in floating-state also are investigated. As a result, the risk elements of neutral ungrounded method as well as neutral floating-phenomenon are removed by installation of separate solidly-grounded transformer and switching four-pole input-breaker to three-pole input breaker.